SMCX, a novel histone demethylase, was recently reported to interact with the newly identified E2F family member, E2F6. E2F6 is believed to regulate the cell cycle through a transcriptional repression mechanism. Preliminary evidence shows that SMCX and E2F6 form a stable complex in cells, and bind to promoters of a subset of E2F6 target genes. The aims of this proposal are to biochemically characterize the SMCX/E2F6 complex and define its biological relevance. The central hypothesis is that E2F6 recruits SMCX to mediate transcriptional repression at target promoters through the dynamics of histone methylation. Thus, the opposing enzymatic activities of histone methyltransferases, and SMCX, a histone demethylase, effect another layer of control for the cell cycle. Techniques including RNAi, chromatin immunoprecipitation, and quantitative PCR will be used to explore the mechanism of the SMCX/E2F6 complex in gene repression. In addition, studies will investigate the regulation of SMCX enzymatic activity and repressive function. Lastly, the biological role of SMCX and E2F6 in regulating cell cycle progression will be examined. These studies will provide a link between epigenetic regulation and cell cycle control. Relevance: SMCX, an epigenetic regulator, associates with E2F6, a protein involved in regulation of cell cycle genes. Inappropriate regulation of the cell cycle can lead to uncontrolled cellular proliferation and cancer. This work explores the contribution of a novel histone demethylase to cell cycle control and tumorigenesis.